The use of a laser-beam-excited fluorescing top dielectric layer of a multi-layered semi-conductor wafer or chip or the like for the purpose of shadowing conductor patterns deposited on controlled flat surfaces thereof, and thereby masking layers therebelow, is described in U.S. Pat. No. 5,278,012 to Yamanaka et al; and improvements thereupon for enabling the use of such techniques with rough or randomly bumpy layers or surfaces and protruding angle conductors is accomplished by the techniques described in my co-pending U.S. patent application Ser. No. 08/880,836, filed Jun. 23, 1997, for "Method Of Optically Inspecting Multi-Layered Electronic Parts And The Like With Fluorescent Scattering Top-Layer Discrimination And Apparatus Therefor".
The use of fluorescence in inspection systems for other purposes has also been taught, as, for example, fluorescing epoxy circuit boards to enable ignoring grainy metallic conductors in structures having high contrast in the visible spectrum (equipment of Orbot Company and others), but not addressing the problem of eliminating images from lower layers. It has further been proposed (Hughes Company) to use television cameras to enable an operator to view, in one large field, the fluorescence of the corner only of wafers located in a cassette, to determine whether resist has been applied or removed from each wafer as a means of process control, as described in the article "High Throughput Inspection Tool For Photoresist Patterning", Semiconductor International, September, 1997.
The present invention, on the other hand, addresses the very much more rigorous and difficult problem of automatically performing a one hundred percent high speed scanning inspection of the complete surface of every wafer for all defects in the resist patterns thereof, such as hairline shorts, pinholes, incorrect line width or spacing or morphology, and for other defects in the patterned resist. The invention, moreover, does so through a novel technique for photoresist fluorescence and automatic image analysis of the whole wafer surface, including defects that, unlike in the television large field-of-view corner inspection of the said article, may represent only a small fraction of the viewed image. As an example, the invention enables a pin hole defect of but one or two pixels to be detected, which would not be detectable in large bright fields of fluorescing resist as in the technique of said article. The invention additionally permits of automatic analysis of the wafer pattern as to its conformity to design rules, known good reference images, and adjacent circuit patterns on the wafer or the like for checking correct pattern morphology, as well.